Unable to access remote server ppk from streamsets.

I used to connect to one of the VM from my Streamsets for accessing the files through SFTP using ppk. All my pipelines are able to access the files through SFTP but when i stopped any pipeline and try to connect to file system the pipeline is giving the exception like "REMOTE_18 - Error accessing remote directory: Could not connect to SFTP server at "sftp://user@myserverip/".
Below is the stacktrace for the same.

com.streamsets.datacollector.runner.PipelineRuntimeException: CONTAINER_0800 - Pipeline 'CLIAVQSFTPTESTINGcopyb5b3d2af-750a-4931-a076-d2e0c456ef34' validation error : REMOTE_18 - Error accessing remote directory: Could not connect to SFTP server at "sftp://username@hostname/".
at com.streamsets.datacollector.execution.runner.common.ProductionPipeline.run(ProductionPipeline.java:128)
at com.streamsets.datacollector.execution.runner.common.ProductionPipelineRunnable.run(ProductionPipelineRunnable.java:75)
at com.streamsets.datacollector.execution.runner.standalone.StandaloneRunner.start(StandaloneRunner.java:724)
at com.streamsets.datacollector.execution.runner.common.AsyncRunner.lambda$start$3(AsyncRunner.java:151)
at com.streamsets.pipeline.lib.executor.SafeScheduledExecutorService$SafeCallable.lambda$call$0(SafeScheduledExecutorService.java:226)
at com.streamsets.datacollector.security.GroupsInScope.execute(GroupsInScope.java:33)
at com.streamsets.pipeline.lib.executor.SafeScheduledExecutorService$SafeCallable.call(SafeScheduledExecutorService.java:222)
at com.streamsets.pipeline.lib.executor.SafeScheduledExecutorService$SafeCallable.lambda$call$0(SafeScheduledExecutorService.java:226)
at com.streamsets.datacollector.security.GroupsInScope.execute(GroupsInScope.java:33)
at com.streamsets.pipeline.lib.executor.SafeScheduledExecutorService$SafeCallable.call(SafeScheduledExecutorService.java:222)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
at com.streamsets.datacollector.metrics.MetricSafeScheduledExecutorService$MetricsTask.run(MetricSafeScheduledExecutorService.java:100)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)